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643 results on '"Wallraven, Christian"'

109. Decoding spatial location of perceived pain to acupuncture needle using multivoxel pattern analysis.

Author

Won-Mo Jung, In-Seon Lee, Ye-Seul Lee, Junsuk Kim, Hi-Joon Park, Wallraven, Christian, and Younbyoung Chae

Subjects
FUNCTIONAL magnetic resonance imaging, PAIN perception, SUPPORT vector machines, ACUPUNCTURE, SOMATOSENSORY cortex
Abstract

The present study applied multivoxel pattern analysis to decode spatial discrimination in pain perception to acupuncture needle from brain functional magnetic resonance image. Fourteen participants were stimulated by acupuncture needles at two adjacent body parts on their left forearm (PC6 vs. HT7). We trained support vector machines on the spatial information from the whole-brain functional magnetic resonance imaging data and projected the support vector machine weight to the brain image space to represent the effect of each voxel on the classifier output. Using region-of-interest masks in individual brains, we trained and tested a linear support vector machine classifier on the accuracy of spatial discrimination in trial-wise functional magnetic resonance imaging data. A classical univariate general linear model analysis testing for differences between the two different locations did not reveal any significant differences. Multivoxel pattern analysis revealed that the brain regions for the prediction of sensory discrimination in pain perceptions to two different points were in the primary somatosensory cortex, primary motor cortex, and supramarginal gyrus, anterior and posterior insula, anterior and posterior cingulate cortex, ventromedial prefrontal cortex, and inferior parietal lobule. Our findings suggest that spatial localizations of pain perceptions to acupuncture needle can be predicted by the neural response patterns in the somatosensory areas and the frontoparietal areas. [ABSTRACT FROM AUTHOR]

Published
2019
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110. Do congenital prosopagnosia and the other-race effect affect the same face recognition mechanisms?

Author

Esins, Janina, Schultz, Johannes, Wallraven, Christian, and Bülthoff, Isabelle

Subjects
Asian, General Commentary, Congenital prosopagnosia, Caucasian, Other-race effect, Behavioral Neuroscience, Psychiatry and Mental health, Neuropsychology and Physiological Psychology, Neurology, other-race effect, Original Research Article, Face recognition, Biological Psychiatry, Neuroscience, congenital prosopagnosia, face recognition
Abstract

Congenital prosopagnosia, an innate impairment in recognizing faces, as well as the other-race effect, a disadvantage in recognizing faces of foreign races, both affect face recognition abilities. Are the same face processing mechanisms affected in both situations? To investigate this question, we tested three groups of 21 participants: German congenital prosopagnosics, South Korean participants and German controls in three different tasks involving faces and objects. First we tested all participants on the Cambridge Face Memory Test in which they had to recognize Caucasian target faces in a 3-alternative-forced-choice task. German controls performed better than Koreans who performed better than prosopagnosics. In the second experiment, participants rated the similarity of Caucasian faces that differed parametrically in either features or second-order relations (configuration). Prosopagnosics were less sensitive to configuration changes than both other groups. In addition, while all groups were more sensitive to changes in features than in configuration, this difference was smaller in Koreans. In the third experiment, participants had to learn exemplars of artificial objects, natural objects, and faces and recognize them among distractors of the same category. Here prosopagnosics performed worse than participants in the other two groups only when they were tested on face stimuli. In sum, Koreans and prosopagnosic participants differed from German controls in different ways in all tests. This suggests that German congenital prosopagnosics perceive Caucasian faces differently than do Korean participants. Importantly, our results suggest that different processing impairments underlie the other-race effect and congenital prosopagnosia.

Published
2014

127. Perception-based Image Interpolation

Author

Stich, Timo, Linz, Christian, Wallraven, Christian, Cunningham, Douglas, and Magnor, Marcus

Subjects
ddc:0, ddc:00, ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION, Veröffentlichung der TU Braunschweig, ddc:006, Article, ComputingMethodologies_COMPUTERGRAPHICS
Abstract

We present a perception-based method for image interpolation, aiming for perceptually convincing transitions between real-world images. Without 3D geometry or scene motion, perception-based image interpolation enables smooth viewpoint navigation across space and time. We show how global visual effects can be created from a collection of unsynchronized, uncalibrated images. A user study confirms the perceptual quality of the proposed image interpolation approach., Technical Report - Computer Graphics Lab, TU Braunschweig, vol. 2008-2-5

Published
2008
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147. Aesthetics by Numbers: Links between Perceived Texture Qualities and Computed Visual Texture Properties.

Author

Jacobs, Richard H. A. H., Haak, Koen V., Thumfart, Stefan, Renken, Remco, Henson, Brian, Cornelissen, Frans W., Spehar, Branka, and Wallraven, Christian

Subjects
AESTHETICS, SEMANTIC differential technique, SURFACE roughness, MATERIALS texture, SENSORY perception
Abstract

Our world is filled with texture. For the human visual system, this is an important source of information for assessing environmental and material properties. Indeed--and presumably for this reason--the human visual system has regions dedicated to processing textures. Despite their abundance and apparent relevance, only recently the relationships between texture features and high-level judgments have captured the interest of mainstream science, despite long-standing indications for such relationships. In this study, we explore such relationships, as these might be used to predict perceived texture qualities. This is relevant, not only from a psychological/neuroscience perspective, but also for more applied fields such as design, architecture, and the visual arts. In two separate experiments, observers judged various qualities of visual textures such as beauty, roughness, naturalness, elegance, and complexity. Based on factor analysis, we find that in both experiments, ~75% of the variability in the judgments could be explained by a two-dimensional space, with axes that are closely aligned to the beauty and roughness judgments. That a two-dimensional judgment space suffices to capture most of the variability in the perceived texture qualities suggests that observers use a relatively limited set of internal scales on which to base various judgments, including aesthetic ones. Finally, for both of these judgments, we determined the relationship with a large number of texture features computed for each of the texture stimuli. We find that the presence of lower spatial frequencies, oblique orientations, higher intensity variation, higher saturation, and redness correlates with higher beauty ratings. Features that captured image intensity and uniformity correlated with roughness ratings. Therefore, a number of computational texture features are predictive of these judgments. This suggests that perceived texture qualities--including the aesthetic appreciation--are sufficiently universal to be predicted--with reasonable accuracy--based on the computed feature content of the textures. [ABSTRACT FROM AUTHOR]

Published
2016
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